Theophylline mitigates the bronchoconstrictor effects of sulfur dioxide in subjects with asthma

Air pollution and resistance to inhaled glucocorticoids: Evidence, mechanisms and gaps to fill

Substantial evidence indicates that cigarette smoke exposure induces resistance to glucocorticoids, the primary maintenance medication in asthma treatment. Modest evidence also suggests that air pollution may reduce the effectiveness of these critical medications. Cigarette smoke, which has clear parallels with air pollution, has been shown to induce glucocorticoid resistance in asthma and it has been speculated that air pollution may have similar effects. However, the literature on an association of air pollution with glucocorticoid resistance is modest to date. In this review, we detail the evidence for, and against, the effects of air pollution on glucocorticoid effectiveness, focusing on results from epidemiology and controlled human exposure studies. Epidemiological studies indicate a correlation between increased air pollution exposure and worse asthma symptoms. But these studies also show a mix of beneficial and harmful effects of glucocorticoids on spirometry and asthma symptoms, perhaps due to confounding influences, or the induction of glucocorticoid resistance. We describe mechanisms that may contribute to reductions in glucocorticoid responsiveness following air pollution exposure, including changes to phosphorylation or oxidation of the glucocorticoid receptor, repression by cytokines, or inflammatory pathways, and epigenetic effects. Possible interactions between air pollution and respiratory infections are also briefly discussed. Finally, we detail a number of therapies that may boost glucocorticoid effectiveness or reverse resistance in the presence of air pollution, and comment on the beneficial effects of engineering controls, such as air filtration and asthma action plans. We also call attention to the benefits of improved clean air policy on asthma. This review highlights numerous gaps in our knowledge of the interactions between air pollution and glucocorticoids to encourage further research in this area with a view to reducing the harm caused to those with airways disease.

An official american thoracic society statement: work-exacerbated asthma

RATIONALE

Occupational exposures can contribute to the exacerbation as well as the onset of asthma. However, work-exacerbated asthma (WEA) has received less attention than occupational asthma (OA) that is caused by work.

OBJECTIVES

The purpose of this Statement is to summarize current knowledge about the descriptive epidemiology, clinical characteristics, and management and treatment of WEA; propose a case definition for WEA; and discuss needs for prevention and research.

METHODS

Information about WEA was identified primarily by systematic searches of the medical literature. Statements about prevention and research needs were reached by consensus.

MEASUREMENTS AND MAIN RESULTS

WEA is defined as the worsening of asthma due to conditions at work. WEA is common, with a median prevalence of 21.5% among adults with asthma. Different types of agents or conditions at work may exacerbate asthma. WEA cases with persistent work-related symptoms can have clinical characteristics (level of severity, medication needs) and adverse socioeconomic outcomes (unemployment, reduction in income) similar to those of OA cases. Compared with adults with asthma unrelated to work, WEA cases report more days with symptoms, seek more medical care, and have a lower quality of life. WEA should be considered in any patient with asthma that is getting worse or who has work-related symptoms. Management of WEA should focus on reducing work exposures and optimizing standard medical management, with a change in jobs only if these measures are not successful.

CONCLUSIONS

WEA is a common and underrecognized adverse outcome resulting from conditions at work. Additional research is needed to improve the understanding of the risk factors for, and mechanisms and outcomes of, WEA, and to inform and evaluate preventive interventions.

Analysis of the concentration-respiratory response among asthmatics following controlled short-term exposures to sulfur dioxide

Some of the most compelling evidence of sulfur dioxide (SO(2))-induced respiratory morbidity is derived from a large body of studies involving controlled short-term exposures among groups of asthmatic volunteers. These studies were extensively cited in the recently completed review of the primary National Ambient Air Quality Standards for SO(2). Although it is clear from these investigations that exposure to SO(2) may result in a significant increase in bronchoconstriction, there is uncertainty regarding the range of concentrations over which this respiratory response occurs. The objective of this study was to better characterize the concentration-response relationship between SO(2) and measures of bronchoconstriction using individual subject lung function response data. In reviewing studies of asthmatics exposed to SO(2) during 5- to 10-min periods of elevated ventilation, we observed clear and consistent evidence of an increase in the bronchoconstrictive response to SO(2) with increasing exposure concentrations between 0.2 and 1.0 ppm. In a subsequent analysis of individual subject data, it was found that those asthmatics experiencing SO(2)-induced respiratory effects at relatively high exposure concentrations are also more likely than nonresponders to experience similar effects after exposure to lower SO(2) concentrations (≤0.4 ppm). Although the clinical significance of these effects is unsettled, the findings provide additional support to epidemiologic evidence of an association between ambient SO(2) concentration and various measures of respiratory morbidity in the general population.

A review of controlled human SO₂ exposure studies contributing to the US EPA integrated science assessment for sulfur oxides

Laboratory studies involving intentional and highly controlled exposures to air pollutants among groups of human volunteers provide valuable information related to the potential health effects of pollutants regulated under the US Clean Air Act. These controlled human exposure studies often provide biological plausibility for the associations between air-pollutant concentration and a given health endpoint observed in epidemiologic investigations. In some cases, results from human laboratory studies provide evidence of a relevant health effect at ambient or near-ambient concentrations and thus directly support the selection of air quality standard levels. In the recently completed review of the US National Ambient Air Quality Standards (NAAQS) for sulfur dioxide (SO₂), the US Environmental Protection Agency (EPA) concluded that short-term exposures to SO₂ are causally associated with an increase in respiratory morbidity. This determination was based in large part on findings from laboratory studies of controlled exposures to SO₂ among small groups of asthmatic individuals. The purpose of this review is to concisely present an overview of the evidence from controlled human exposure studies of SO₂-induced respiratory health effects following short-term exposures. While the majority of these studies were conducted over 20 years ago, the findings and insights gained from this work continues to play an integral role in evaluating the respiratory effects of ambient exposures to SO₂.

Traffic, outdoor air pollution, and asthma

The epidemiology of asthma and outdoor air pollution has shown that respiratory health effects can vary in relation to different emission sources, types of pollutants, underlying nutritional status, medication use, and genetic polymorphisms. Using sophisticated exposure assessment methods in conjunction with clinical tests and biomarkers that provide mechanistic information, the study of outdoor epidemiology and asthma has evolved into a complex multidisciplinary field. This article presents an overview of the mechanisms by which outdoor air pollution and traffic-related emissions lead to changes in respiratory health and lung function in subjects with asthma.

Protective effect of ipratropium bromide on bronchoconstriction induced by sulfur dioxide exposure during apricot sufurization processes that causes asthma-like syndrome in agricultural environment

We previously showed that apricot sulfurization workers are exposed to high concentrations of sulfur dioxide (SO2), resulting in an asthma-like syndrome. The aim of this study was to investigate whether pre-treatment of ipratropium bromide protects bronchoconstriction induced by SO2 exposure during apricot sulfurization processes that causes asthma-like syndrome. Firstly, pulmonary function tests were measured before and immediately after SO2 exposure due to processes of apricot sulfurization in 21 healthy volunteer apricot sulfurization workers who did not use any medication in apricot farms. One week later, same measurements were repeated in the same workers when they were working in same farm but they were administered two puffs of ipratropium bromide (20 microg per dose) before 30 min second SO2 exposure for protection of SO2-induced bronchoconstriction. Occupational SO2 exposure caused significant decrement in forced vital capacity (FVC), forced expiratory volume (FEV1) and forced mid-expiratory flow rate (FEF25-75%) in the worker and these decrements were prevented by ipratropium bromide given 30 min before SO2 exposure. This result suggests that pre-treatment of ipratropium bromide protects SO2-induced bronchoconstriction in healthy worker during apricot sulfurization processes that causes asthma-like syndrome in agricultural environment.

The role of air pollution in asthma and other pediatric morbidities

A growing body of research supports the role of outdoor air pollutants in acutely aggravating chronic diseases in children, and suggests that the pollutants may have a role in the development of these diseases. This article reviews the biologic basis of children's unique vulnerability to highly prevalent outdoor air pollutants, with a special focus on ozone, respirable particulate matter (PM 2.5 [<2.5 microm in diameter] and PM 10 [<10 microm in diameter]), lead, sulfur dioxide, carbon monoxide, and nitrogen oxides. We also summarize understanding regarding health effects and molecular mechanisms of action. Practitioners can significantly reduce morbidity in children and other vulnerable populations by advising families to minimize pollutant exposures to children with asthma, or at a broader level by educating policymakers about the need to act to reduce pollutant emissions. Management of children with asthma must expand beyond preventing exposures to agents that directly cause allergic reactions (and therefore can be diagnosed by means of skin tests) and must focus more attention on agents that cause a broad spectrum of nonspecific, generalized inflammation, such as air pollution.

Pulmonary function changes and immunomodulation of Th 2 cytokine expression induced by aminophylline after sensitization and allergen challenge in brown Norway rats

BACKGROUND AND OBJECTIVE

Evidence has shown that aminophylline has bronchoprotective, anti-inflammatory, and immunomodulatory effects. Our purpose was to evaluate the effect of different doses of aminophylline on the late-phase reaction, bronchial hyperresponsiveness (BHR) and T cell-related cytokine mRNA expression in brown Norway rats induced by ovalbumin (OA) sensitization.

METHODS

Forty rats were equally divided into four groups. Groups I, II, and III animals were sensitized and subsequently provoked with OA. Aminophylline 25 mg/kg was given intraperitoneally to the group I animals and 5 mg/kg to group II animals. Group III animals received intraperitoneal normal saline. Group IV breathed aerosolized saline as a control. After OA provocation, the animals were anesthetized. Pulmonary function tests were performed at baseline and after varying doses of acetylcholine. Thereafter, bronchoalveolar lavage was performed and the lungs were examined histologically. Total RNA was extracted from lung tissue and reverse transcriptase-polymerase chain reaction was performed using primers for interleukin (IL)-2, IL-4, IL-5, IL-6, IL-10, interferon-gamma, inducible nitric oxide synthase, and beta-actin.

RESULTS

Group III had worse pulmonary function tests, more severe BHR, and more severe lung inflammation, higher IL-4 and IL-10 cytokine levels in bronchoalveolar lavage fluid, and higher IL-4, IL-5, IL-6, IL-10, tumor necrosis factor-alpha and inducible nitric oxide synthase mRNA expression than the other three groups. Expression of IL-2 and interferon-gamma was significantly reduced in group III.

CONCLUSIONS

Both low and high dose aminophylline are effective in preventing late-phase bronchoconstriction, BHR, and an inflammatory response. Aminopylline decreases T helper cell 2-related cytokine mRNA expression but increases T helper cell 1-related cytokines mRNA expression.

Respiratory effects of air pollution on allergic disease

Allergic patients have an increased susceptibility to the adverse effects of both natural and man-made air pollutants. This goes for both indoor and outdoor air pollutants and manifests itself with biochemical, cellular, and pathophysiologic expressions of adverse health effects in allergic individuals. Also occupationally induced allergic diseases will remain very important. This area has been reviewed recently by Cullen et al. Since allergic patients comprise somewhere between 15% and 20% of the population, this increased susceptibility is of crucial importance not only for medical care and research but for legislative and regulatory consideration to protect these vulnerable individuals.